**Core Concept**
The question tests knowledge of **routes of administration** for general anaesthesia, focusing on the most commonly used method. General anaesthesia requires a rapid and reliable onset of action, which is typically achieved through **intravenous** or **inhalational** routes.

**Why the Correct Answer is Right**
Although the correct answer choice is missing, the most common route for inducing general anaesthesia is **intravenous**, using drugs like propofol, due to its rapid onset and ease of administration. This route allows for precise control over the dose and effect of the anaesthetic agent.

**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific answer choices, it's challenging to provide detailed incorrect option analysis. However, typically, incorrect options might include less common routes such as oral or topical for general anaesthesia induction.
**Option B:** Similarly, without specifics, we can say that if an option suggests an inappropriate route like intramuscular for rapid induction, it would be incorrect due to slower onset times.

**Why Each Wrong Option is Incorrect (Continued)**
**Option C:** and **Option D:** Assuming these might represent other less common or inappropriate routes for general anaesthesia induction, they would be incorrect for similar reasons related to onset time, control, and standard practice.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the choice of anaesthetic route depends on the **specific requirements of the surgical procedure** and the **patient's health status**. For general anaesthesia, **intravenous induction** is often preferred for its rapid effect and controllability.

**Correct Answer:** Correct Answer: D. Intravenous.